Very large antenna array systems, such as massive multiple input multiple output (MIMO) systems, provide the opportunity for spatial division multiple access (SDMA) in which each individual user may be served with the same time-frequency resource as other users. This multiple access technique requires accurate and coherent control of both amplitude and phase over the antenna array and is a promising technique with potential to increase spectral efficiency in wireless communication systems.
Massive MIMO is also applicable in radio detection and ranging (RADAR) systems, where it offers potential to increase detection performance of the RADAR system.
Large antenna array systems comprise many antenna elements, and since each antenna element often has dedicated transmit circuitry, comprising, e.g., a digital to analog converter (DAC) and power amplifier (PA), a trade-off is often necessary between the cost of the array in terms of, e.g., power consumption and production cost on one hand, and transmitter performance in terms of, e.g., distortion or efficiency on the other hand.
Consequently, some present antenna arrangements configured for digital beam-forming of a transmit signal are either associated with large cost, or are constrained in terms of spatial duplexing ability due to excessive transmit signal distortion or otherwise limited hardware capabilities.
Thus, at least partly due to the above, there is a need for alternative distortion mitigation methods for use in antenna array systems, allowing for low-cost antenna arrays with spatial duplexing ability.